Gear assembly for motor vehicle

ABSTRACT

A gear assembly for a motor vehicle includes first clutch configured to selectively couple an input shaft to an output shaft and a second clutch configured to selectively couple the input shaft to a planetary gear train. When the first clutch is activated and the second clutch is not activated, the input torque is transmitted from the input shaft to the output shaft such that the output torque relative to the input torque is a first gear ratio. When the second clutch is activated and the first clutch is not activated, the input torque is transmitted from the input shaft to the output shaft through the planetary gear train such that the output torque relative to the input torque is a second gear ratio. When neither the first clutch nor the second clutch are activated, the input torque is not transmitted from the input shaft to the output shaft.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 61/282,339, filed on Jan. 26, 2010, thedisclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

The present application relates generally to the field of drive trainsfor motor vehicles. More specifically, the present application relatesto a dual gear system which provides power in one of two gear ratios tothe coupled driving wheels.

There is an ever increasing need for higher efficiency from powertrainsof motor vehicles, due to increasing energy prices and increasingregulations, such as government Corporate Average Fuel Economy (CAFE)standards. It would be advantageous for a powertrain or gear system toprovide higher efficiency over a broad range of speeds and torques. Thusit would be useful for the gear system of a motor vehicle to includemore gears that are able to improve efficiency and to improveperformance by providing higher torque across a wide range of speeds.

SUMMARY

According to an exemplary embodiment, a gear assembly for a motorvehicle includes an input shaft configured to rotate about an axis ofrotation, wherein the input shaft includes a first end configured toreceive input torque from a first vehicle component and a second endconfigured to transmit torque. An output shaft is configured to rotateabout the axis of rotation, wherein the output shaft includes a firstend configured to transmit output torque to a second vehicle componentand a second end configured to receive torque. A planetary gear train isconfigured to provide output torque to the output shaft, wherein theplanetary gear train includes a ring gear, a sun gear, a plurality ofplanet gears, and a carrier. A first clutch is configured to selectivelycouple the input shaft to the output shaft to transmit torque, and asecond clutch configured to selectively couple the input shaft to theplanetary gear train. When the first clutch is activated and the secondclutch is not activated, the input torque is transmitted from the inputshaft to the output shaft such that the output torque relative to theinput torque is a first gear ratio. When the second clutch is activatedand the first clutch is not activated, the input torque is transmittedfrom the input shaft to the output shaft through the planetary geartrain such that the output torque relative to the input torque is asecond gear ratio. When neither the first clutch nor the second clutchare activated, the input torque is not transmitted from the input shaftto the output shaft.

According to another exemplary embodiment, a gear assembly for a motorvehicle includes an input shaft including a first end configured toreceive input torque from a first vehicle component and a second endconfigured to transmit torque and an output shaft including a first endconfigured to transmit output torque to a second vehicle component and asecond end configured to receive torque. A planetary gear train includesa ring gear, a sun gear, a plurality of planet gears, and a carrier. Aslide member is rotationally coupled to the input shaft to receive inputtorque. The slide member is configured to slide between a first positionand a second position in a sliding direction relative to the second endof the input shaft. At the first position, the slide member engages theplanetary gear train to transmit torque from the input shaft to theoutput shaft through the slide member and planetary gear train such thatthe output torque relative to the input torque is a first gear ratio. Atthe second position, the slide member engages the output shaft withoutengaging the planetary gear train to transmit torque from the inputshaft to the output shaft through the slide member such that the outputtorque relative to the input torque is a second gear ratio. When theslide member is between the first and second positions, the slide memberengages neither the planetary gear train nor the output shaft, and theinput torque is not transmitted from the input shaft to the outputshaft.

According to another exemplary embodiment, a gear assembly for a motorvehicle includes an input shaft configured to rotate about an axis ofrotation and an output shaft configured to rotate about the axis ofrotation. A planetary gear train is configured to receive torque fromthe input shaft, wherein the planetary gear train includes a ring gearconnected to the input shaft, a sun gear, a plurality of planet gears,and a carrier configured to transmit output torque. A clutch isconfigured to selectively couple the output shaft and the planetary geartrain. When the clutch is activated, the output shaft and the carrierrotate together about the axis of rotation, and the input torque istransmitted from the input shaft through the planetary gear train to theoutput shaft, so that the output torque relative to the input torque isa first gear ratio. When the clutch is not activated, the carrier isdecoupled from the output shaft but the sun gear is coupled to theoutput shaft, and the input torque is transmitted from the input shaftto the output shaft through the planetary gear train, so that the outputtorque relative to the input torque is a second gear ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary embodiment of a dual gearassembly.

FIG. 2 is a cross-sectional view of the dual gear assembly of FIG. 1.

FIG. 3 is another cross-sectional view of the dual gear assembly of FIG.1.

FIG. 4 is a perspective view of another exemplary embodiment of a dualgear assembly.

FIG. 5 is a cross-sectional view of the dual gear assembly of FIG. 4.

FIG. 6 is another cross-sectional view of the dual gear assembly of FIG.4, shown in its neutral position.

FIG. 7 is a cross-sectional view of another exemplary embodiment of adual gear assembly.

FIG. 8 is a cross-sectional view of yet another exemplary embodiment ofa dual gear assembly.

DETAILED DESCRIPTION

As shown in FIG. 1, a dual gear assembly 20 according to an exemplaryembodiment is illustrated and may be used within a motor vehicle toprovide two gear ratios. The dual gear assembly 20 may be coupled to theoutput of a conventional transmission having a specified number of gearratios (e.g., six gear ratios) to provide the vehicle with twice thenumber of gear ratios provided by the conventional transmission. Forexample, a vehicle having a conventional transmission with six gearratios coupled to a dual gear assembly would have a total of twelve gearratios. This provides the vehicle with improved efficiency and withimproved power over a broad range of speeds. Accordingly, anytransmission having any number of specified gear ratios may be coupledto the dual gear assemblies as described herein to provide suchimprovements. Additionally, according to other exemplary embodiments,the dual gear assemblies as described herein may be coupled directly tothe output from the engine, such as the driveshaft.

As shown in FIGS. 2 and 3, the dual gear assembly 20 includes an inputshaft 23 that is configured to rotate about an axis of rotation 21, atleast one bearing 28, a housing 29, a planetary gear train (PGT) 30, afirst clutch 40, a second clutch 50, an output shaft 60, and a drive (orlinking) member 90. According to an exemplary embodiment, the inputshaft 23 may be made from steel or some other suitable material strongenough to transmit or communicate torque from the engine or transmissionof a motor vehicle. The input shaft 23 may be configured as a tube or ashaft, and includes a first end 24 configured to engage the engine, thetransmission, or a driveshaft transmitting torque from either the engineor transmission, and a second end 25. The inner surface of the secondend 25 of the input shaft 23 may be rotationally coupled to the bearing28, which may be rotationally coupled to the housing 29, so that thesecond end 25 may rotate about the axis of rotation 21 relative to thehousing 29. The outer surface of the second end 25 of the input shaft 23may be rotationally coupled to the inner surface of the drive member 90,so that rotation of the input shaft 23 about the axis of rotation 21rotates the drive member 90 about the axis of rotation 21 withsubstantially the same frequency and torque. According to an exemplaryembodiment, the second end 25 may include external splines that engageinternal splines of drive member 90. According to another exemplaryembodiment, the second end 25 may be welded, fastened, or anycombination thereof to the drive member 90.

The drive member 90 may be coupled to the first clutch 40, so thatactuation of the first clutch 40 may selectively couple the drive member90 to or decouple the drive member 90 from the output shaft 60, thuscausing the output shaft 60 to rotate with substantially the samefrequency, torque, and power as the coupled input shaft 23 and drivemember 90. The first clutch 40 may be actuated by a first clutch piston41, which may be controlled by a first hydraulic assembly 42. Fluidpressure produced by the hydraulic assembly 42 displaces the firstclutch piston 41 from a first non-coupled position to a second coupledposition. In the first non-coupled position, the drive member 90 isdecoupled (or disengaged) from the output shaft 60, such that no torqueor rotation is transmitted or communicated to the output shaft 60. Inthe second coupled position, the drive member 90 is coupled (or engaged)to the output shaft 60 through an engaging feature 43. Thus, theengaging feature 43 couples the drive member 90 to the output shaft 60so that rotation of the drive member 90 about the axis of rotation 21rotates the output shaft 60 about the axis of rotation 21 withsubstantially the same frequency and torque.

According to an exemplary embodiment, the output shaft 60 may rotateabout the axis of rotation 21 and may be made of steel or some otheruseful material strong enough to transmit or communicate torque fromanother component or member of gear system 20. The output shaft 60includes a first end 61 and a second end 65, and may be configured as atube having an inner diameter coupled to the outer diameter of at leastone bearing 28, which may then have an inner diameter coupled to theouter diameter of input shaft 23. Thus, the output shaft 60 and inputshaft 23 are substantially concentric and configured to rotatesubstantially about the axis of rotation 21. The output shaft 60 mayrotate with the same torque, frequency, and power relative to the inputshaft 23 or may rotate with a different torque, frequency, and powerrelative to the input shaft 23, depending on the mode of operation ofthe dual gear assembly 20. The outer diameter of the output shaft 60 maybe coupled to the inner diameter of at least one bearing 28, which mayhave an outer diameter coupled to a member of the PGT 30, to the housing29, to another vehicle component, or any combination thereof. The firstend 61 of the output shaft 60 includes a coupling feature 62 configuredto transmit or communicate torque to another member, such as a pinionshaft, rear differential, or rear axle. According to an exemplaryembodiment, the coupling feature 62 includes splines that engage amating member. However, the coupling feature 62 may utilize any methodof communicating torque to another rotating member may be used.

The second end 65 of the output shaft 60 is configured to have a gearreduced coupling 66 and a direct coupling 67. According to an exemplaryembodiment, the second end 65 of the output shaft 60 is configured tohave more than one outer diameter (i.e., a stepped or shouldered end),where the gear reduced coupling 66 is located on one step and includesexternal splines or gear teeth to engage a member of the PGT 30, andwhere the direct coupling 67 is located on a second step and includessplines or gear teeth to engage the engaging feature 43 of the firstclutch 40.

The PGT 30 includes a ring gear 31, a plurality of planet gears 32, acarrier 33, and a sun gear 34. According to an exemplary embodiment, thesun gear 34 is held stationary or fixed, while the ring gear 31 providesinput power or torque to the PGT 30 through the second clutch 50 fromthe drive member 90, and the carrier 33 provides gear-reduced outputpower or torque to the output shaft 60. According to an exemplaryembodiment, the ring gear 31 may rotate substantially about the axis ofrotation 21 and includes internal gear teeth that engage the pluralityof planet gears 32, and a coupling member 38, which includes internalsplines or gear teeth that may be selectively coupled to the secondclutch 50. According to an exemplary embodiment, each planet gear 32includes external gear teeth, which engage the internal gear teeth ofthe ring gear 31 and the external gear teeth of the sun gear 34simultaneously, and a pivot axis or an axis of rotation 35, where eachpivot axis 35 may be coupled to the carrier 33. Thus, each planet gear32 rotates about its pivot axis 35 relative to the carrier 33, and theplurality of planet gears 32 rotate together with the carrier 33 aboutthe axis of rotation 21 relative to the sun gear 34.

According to an exemplary embodiment, the carrier 33 includes aplurality of apertures for coupling the plurality of planet gears 32,where each aperture is substantially concentric to the pivot axis 35 ofone of the plurality of planet gears 32. The carrier 33 further includesa gear-reduced coupling 36 having an inner diameter that forms anaperture substantially concentric to the axis of rotation 21 and havinginternal gear teeth coupled to the external gear teeth of thegear-reduced coupling 66 of the output shaft 60. Thus, the carrier 33and output shaft 60 rotate about the axis of rotation 21 withsubstantially the same torque, frequency, and power. According to anexemplary embodiment, the sun gear 34 includes external gear teeth,which engage the external gear teeth of the planet gears 32, and afixing member 37 coupled to the housing 29 of the dual gear assembly 20,which prohibits rotation of the sun gear 34 relative to the housing 29.

According to this embodiment, the sun gear 34 rotates with an angularvelocity of ω_(s) (where ω_(s) is zero, for the configuration shown inFIGS. 2 and 3, being fixed to housing 29) having the number of gearteeth N_(s), the ring gear 31 rotates with an angular velocity of ω_(r)having the number of gear teeth N_(r), and the carrier 33 rotates withan angular velocity of ω_(c) having the number of gear teeth N_(c). Thegear ratio (i_(rc)) for this configuration may be calculated as follows:

$i_{rc} = {\frac{\omega_{r}}{\omega_{c}} = {{1 + \frac{N_{s}}{N_{r}}} \geq 1}}$

According to another embodiment, the PGT may include the ring gear heldstationary or fixed, the sun gear providing input power or torque to PGTthrough a second clutch from a drive member, and the carrier providingoutput power or torque to an output shaft. According to anotherembodiment, the PGT may include a carrier held stationary or fixed, thesun gear providing input power or torque to PGT through a second clutchfrom a drive member, and the ring gear providing output power or torqueto an output shaft.

The drive member 90 may be coupled to the second clutch 50, so thatactuation of the second clutch 50 may selectively couple the drivemember 90 to the coupling member 38 of the ring gear 31 of the PGT 30,inducing the ring gear 31 to rotate with the same frequency, torque, andpower as the coupled input shaft 23 and drive member 90. The secondclutch 50 may be actuated by a second clutch piston 51, which may becontrolled by a second hydraulic assembly 52. Fluid pressure produced bythe hydraulic assembly 52 displaces the second clutch piston 51 from afirst non-coupled position to a second coupled position. In the firstnon-coupled position, the drive member 90 is decoupled (or disengaged)form the coupling member 38 of the ring gear 31 of the PGT 30, such thatno torque or power is transmitted or communicated. In the second coupledposition, the drive member 90 is selectively coupled (or engaged) to thering gear 31 of the PGT 30 through the engaging feature 53 of the secondclutch 50, which selectively engages coupling member 38, so thatrotation of the drive member 90 about the axis of rotation 21 rotatesthe ring gear 31 about the axis of rotation 21 with substantially thesame frequency, torque, and power.

According to an exemplary embodiment, the dual gear assembly 20 hasthree operating configurations. The first configuration is a neutralconfiguration, where the drive member 90 is coupled internally to theinput shaft 23 and receives torque, but neither the first clutch 40 northe second clutch 50 is engaged, so the drive member 90 is not coupledexternally and does not communicate torque or power to the output shaft60. The second configuration is a direct connection configuration, wherethe first clutch 40 is engaged, but the second clutch 50 is not engaged,so the drive member 90 is coupled externally to the direct coupling 67of the second end 65 of the output shaft 60 and coupled internally tothe input shaft 23. Thus, the second (or direct connection)configuration of the dual gear assembly 20 outputs substantially thesame torque and power relative to the torque and power that are inputinto the assembly. The third configuration is a gear-reductionconfiguration, where the second clutch 50 is engaged, but the firstclutch 40 is not engaged, so the drive member 90 is coupled externallyto the coupling member 38 of the ring gear 31 of the PGT 30, and coupledinternally to the input shaft 23. Thus, the third (or gear-reduced)configuration of the dual gear assembly 20 outputs torque and power thatare gear-reduced by the PGT 30 relative to the torque and power that areinput into the assembly.

As shown in FIG. 4, a dual gear assembly 120 according to anotherexemplary embodiment is illustrated and may be used within a motorvehicle to provide two gear ratios. The dual gear assembly 120 may becoupled to the output of a conventional transmission having a specifiednumber of gear ratios, so that the vehicle having this configurationwould have as the total number of gear ratios, twice the number of gearratios of the conventional transmission.

As shown in FIGS. 5 and 6, the dual gear assembly 120 includes an inputshaft 123 that is configured to rotate about an axis of rotation 121, atleast one bearing 128, a housing 129, a planetary gear train (PGT) 130,an output shaft 160, a synchronizer assembly 170, an actuator assembly180, and a slide or slide member 190. According to an exemplaryembodiment, the input shaft 123 may be made from steel or some othersuitable material strong enough to transmit or communicate torque andpower from the engine or transmission of a motor vehicle. The inputshaft 123 may be configured as a tube or a shaft, and may have a firstend 124 configured to engage the engine, the transmission, or adriveshaft transmitting torque from either the engine or transmissionand a second end 125. The second end 125 of the input shaft 123 mayinclude external splines configured to couple to internal splines of theslide member 190, so that the slide member 190 is rotationally coupledto the input shaft 123, but may slide axially along the axis of rotationrelative to the input shaft 123. Thus, slide member 190 rotates withsubstantially the same torque and frequency as the input shaft 123.

The output shaft 160 may rotate about axis of rotation 121 and may bemade of steel or some other suitable material strong enough to transmitor communicate torque from another component or member of the dual gearsystem 120. According to an exemplary embodiment, the output shaft 160includes a first end 161 and a second end 165, and may be configured asa tube having an inner diameter coupled to the outer diameter of atleast one bearing 128, which has an inner diameter coupled to the outerdiameter of the input shaft 123. Thus, the output shaft 160 and inputshaft 123 are substantially concentric and both rotate substantiallyabout the axis of rotation 121. The output shaft 160 may rotate aboutthe bearing(s) 128 with a different torque, frequency, and powerrelative to the input shaft 123, or the output shaft 160 may rotateabout bearing(s) 128 with the same torque, frequency, and power relativeto the input shaft 123, depending on the operating configuration of thedual gear system 120. The first end 161 of the output shaft 160 includesa coupling feature 162 having splines configured to transmit orcommunicate torque to another member, such as a pinion shaft 117 (shownin FIG. 5), rear differential, or rear axle. According to an exemplaryembodiment, the second end 165 of the output shaft 160 is configured tocouple to the carrier 133 of the PGT 130, so that the output shaft 160and carrier 133 rotate with substantially the same torque, frequency,and power about the axis of rotation 121. The second end 165 and thecarrier 133 may be coupled by any useful method, such as splines, whichcan transmit or communicate torque. According to another exemplaryembodiment, the output shaft 160 and the carrier 133 of the PGT 130 areconfigured to be one-piece (i.e., manufactured to be the same component)and thus rotate as one, having the same torque, frequency, and power.This embodiment of the output shaft 160 may be configured so that thecarrier 133 extends from its second end 165, where the output shaft 160forms an integral part of the PGT 130.

The PGT 130 includes a ring gear 131, a plurality of planet gears 132, acarrier 133, and a sun gear 134. According to an exemplary embodiment,the sun gear 134 is held stationary or fixed, while the ring gear 131provides input power or torque to the PGT 130 through engagement of theslide member 190, and the carrier 133 provides gear-reduced output poweror torque to the output shaft 160. According to an exemplary embodiment,the ring gear 131 may rotate substantially about the axis of rotation121 and includes internal gear teeth, which engage the plurality ofplanet gears 132, and a coupling member 138, which has an inner diameterthat includes splines or gear teeth that may selectively couple to theslide member 190. According to an exemplary embodiment, each planet gear132 includes external gear teeth, which engage the internal gear teethof the ring gear 131 and the external gear teeth of the sun gear 134simultaneously. Accordingly, each planet gear 132 rotates about anindependent pivot axis or its own axis of rotation 135. Additionally,each planet gear 132 may include an inner diameter, which may be coupledto the carrier 133. Thus, each planet gear 132 rotates about its pivotaxis 135 relative to the carrier 133, and the plurality of planet gears132 rotate together with the carrier 133 about the axis of rotation 121relative to the sun gear 134. According to an exemplary embodiment, thecarrier 133 includes a plurality of apertures for coupling the pluralityof planet gears 132, where each aperture is substantially concentric tothe pivot axis 135 of one of the plurality of planet gears 132.According to an exemplary embodiment, the sun gear 134 includes externalgear teeth, which engage the external gear teeth of the plurality ofplanet gears 132, and a fixing member 137 coupled to the housing 129 ofthe dual gear assembly 120, which prohibits rotation of the sun gear 134relative to the housing 129.

The slide member 190 includes a first end 191 and a second end 195, andis configured to move between a first position and a second positionalong sliding direction 199 when driven by an actuator 182 of theactuator assembly 180. The first end 191 of the slide member 190 mayinclude an outer engaging feature 192 for selectively engaging to thecoupling member 138 of the ring gear 131, and an inner engaging feature193 for coupling to the external splines of the intermediate member 122and for selectively engaging the synchronizer 170. According to anexemplary embodiment, the intermediate member 122 may be formed separateto the input shaft 123 and may include internal splines for coupling andtransmitting torque to the second end 125 of the input shaft 123.According to another exemplary embodiment, the intermediate member 122may be integrally formed with the second end 125 of the input shaft 123to include external splines that may be rotationally coupled to theinternal splines to the inner engaging feature 193 of the slide member190, so that torque and power are transmitted or communicated from theinput shaft 123 to the slide member 190 through the intermediate member122. According to an exemplary embodiment, the outer engaging feature192 may include external splines for selectively engaging the internalsplines of the coupling member 138, and the inner engaging feature 193may include internal splines for engaging the external splines of thesecond end 125 of the input shaft 123 and for selectively engaging theexternal splines of the synchronizer 170.

The second end 195 of the slide member 190 may include a couplingfeature 196, which couples to the actuator 182. According to anexemplary embodiment, coupling feature 196 may be an axial couple, suchas a detent or other shape, to allow rotation of the slide member 190about the axis of rotation 121 relative to the actuator 182, but wheredisplacement of the actuator 182 along the sliding direction 199displaces the slide member 190 with substantially the same displacementas the actuator 182. According to another exemplary embodiment, thecoupling feature 196 may be a rigid couple, where rotation of the slidemember 190 about the axis of rotation 121 induces substantially the samerotation into the actuator 182, and where displacement of the actuator182 along the sliding direction 199 displaces the slide member 190 withsubstantially the same displacement as the actuator 182.

Displacement of the slide member 190 and actuator 182 may be induced bythe actuator assembly 180, which includes a piston 181 and an actuator182. According to an exemplary embodiment, the piston 181 may beconfigured to produce a force generated by varying its pneumaticpressure to displace the actuator 182 along the axis of rotation 121.According to another exemplary embodiment, the piston 181 may beconfigured to produce a force generated by varying its hydraulicpressure to displace the actuator 182. Thus, fluid pressure in thechamber housing the piston 181 may be increased to produce a force thatdisplaces the piston 181 along a line that may be substantially parallelto the axis of rotation 121, where the actuator 182 may be displaced bythe piston 181 from a first position to a second position, or to aneutral position (i.e., position between first and second positions).This displacement of the actuator 182 induces displacement of the slidemember 190 from a first position to a second position, or to a neutralposition. When the slide member 190 is in its first position, the innerengaging feature 193 is coupled to the input shaft 123 and the outerengaging feature 192 is coupled to the coupling member 138 of the ringgear 131. Thus, torque transmits or communicates from the input shaft123 into the ring gear 131 of the PGT 130 through the slide member 190,so the output torque and power of the output shaft 160 are gear-reducedthrough the PGT 130. When the slide member 190 is in its secondposition, the inner engaging feature 193 is coupled to the input shaft123 and is further coupled to the output shaft 160 through thesynchronizer 170, while the outer engaging feature 192 is decoupled.Thus, torque transmits or communicates from the input shaft 123 to theoutput shaft 160 through the slide member 190 and the synchronizer 170,so that output torque and power are not gear-reduced. When the slidemember 190 is in its neutral position, the inner engaging feature 193 iscoupled only to the input shaft 123 and the outer engaging feature 192is decoupled. Thus, no torque or power are transmitted or communicatedto the output shaft 160.

The actuator assembly 180 may further include a biasing member 183, suchas a coil spring, that may produce a force in the directionsubstantially opposite to the force generated by the piston 181. Whenthe pressure in the piston 181 is reduced to a predetermined amount thatproduces a force having a lower magnitude relative to the force producedby the biasing member 183, then the actuator 182 may be displaced fromits second position to its first position. According to anotherembodiment, the piston 181 may displace the actuator 182 and/or slidemember 190 from its second position (i.e., where torque is notgear-reduced) to its first position (i.e., where torque is gear-reducedthrough the PGT 130) and where the biasing member 183 is configured todisplace the actuator 182 and/or slide member 190 from its firstposition to its second position.

The dual gear assembly 120 may have three operating configurations. Thefirst configuration is a neutral configuration, where the input shaft123 is decoupled from the output shaft 160. The second configuration isa direct connection configuration, where the input shaft 123 is coupleddirectly to the output shaft 160 through synchronizer 170 by the slidemember 190. Thus, the second configuration of the dual gear assembly 120outputs substantially the same torque and power relative to the torqueand power that is input into the assembly. The third configuration is agear-reduction configuration, where the input shaft 123 is coupled tothe output shaft 160 through the PGT 130 by the slide member 190. Thus,the third configuration of the dual gear assembly 120 outputs torque andpower that are gear-reduced by the PGT 130 relative to the torque andpower that are input into the assembly.

As shown in FIG. 7, the dual gear assembly 220 according to anotherexemplary embodiment is illustrated and includes an input shaft 223 thatis configured to rotate about an axis of rotation 221, at least onebearing 228, a housing 229, a planetary gear train (PGT) 230, a firstclutch 240, a second clutch 250, an output shaft 260, and a linkingmember 290. According to an exemplary embodiment, the input shaft 223may be made from steel or some other suitable material strong enough totransmit or communicate torque from the engine or transmission of amotor vehicle. The input shaft 223 may be configured as a tube or ashaft, and may have a first end 224 configured to engage a memberproviding input torque and power. The input shaft 223 may furtherinclude a second end 225, having external splines 227, which engageinternal splines 291 of the linking member 290. Thus, the input shaft223 is coupled to linking member 290, so that both the input shaft 223and linking member 290 rotate about the axis of rotation 221 withsubstantially the same torque, frequency, and power. According to anexemplary embodiment, the linking member 290 further includes a firsthydraulic cavity or line 294 and a second hydraulic cavity or line 295,which may be used to bring hydraulic fluid to the first and secondpistons 241, 251 of the first and second clutches 240, 250,respectively.

According to an exemplary embodiment, the first clutch 240 and secondclutch 250 may be coupled to the linking member 290 to rotate about theaxis of rotation 221 with substantially the same torque and frequency asthe linking member 290. Actuation of the first clutch 240 mayselectively couple the linking member 290 directly to the output shaft260, inducing the output shaft 260 to rotate with substantially the sametorque, frequency, and power of the input shaft 223. Actuation of thesecond clutch 250 may selectively couple the linking member 290 to theoutput shaft 260 through the PGT 230, inducing the output shaft 260 torotate with a torque and power that are gear-reduced through the PGT 230relative to the torque and power of the input shaft 223.

The first clutch 240 includes an engaging feature 243, which may beselectively engaged to (or brought into contact with) the output shaft260 through friction, and a first piston 241 configured to produce aforce that induces the friction between the engaging feature 243 and theoutput shaft 260. The engaging feature 243 may be displaced by the forceof the piston 241 into contact with the output shaft 260 to inducefriction between the engaging feature 243 of the first clutch 240 andthe output shaft 260, thereby resulting in the coupling of the linkingmember 290 to the output shaft 260 through the first clutch 240. Whenthe force from the piston 241 is removed, the engaging features 243 ofthe first clutch 240 may be disengaged from (or brought out of contactwith) the output shaft 260, thereby removing the friction between theengaging feature 243 and the output shaft 260 and decoupling the linkingmember 290 from the output shaft 260. According to an exemplaryembodiment, first clutch 240 may be configured so that the force exertedby the first piston 241 may be controlled by varying the hydraulicpressure or hydraulic fluid in first hydraulic line 294 from a firsthydraulic pump or assembly (not shown). The force from the first piston241 may displace the engaging feature 243, so that the engaging feature243 is selectively coupled to the direct coupling 267 of the outputshaft 260. Thus, the first piston 241 of the first clutch 240 may beactuated to couple the linking member 290 to the output shaft 260through the first clutch 240, so that the input shaft 223 and the outputshaft 260 rotate with substantially the same torque, frequency, andpower.

The second clutch 250 includes an engaging feature 253, which may beselectively engaged to (or brought into contact with) the couplingmember 238 of the ring gear 231 of the PGT 230 through friction, and asecond piston 251 configured to produce a force that induces thefriction between the engaging feature 253 and the coupling member 238.The engaging feature 253 may be displaced by the force of the piston 251into contact with the coupling member 238 to induce friction between theengaging feature 253 of the second clutch 250 and the coupling member238 of the PGT 230, thereby resulting in the coupling of the linkingmember 290 to the PGT 230 (and to the output shaft 260 that is alsoconnected to the PGT 230) through the second clutch 250. When the forcefrom the piston 251 is removed, the engaging feature 253 of the secondclutch 250 may be disengaged from (or brought out of contact with) thecoupling member 238, thereby removing the friction between the engagingfeature 253 and the coupling member 238 and decoupling the linkingmember 290 from the PGT 230. According to an exemplary embodiment, thesecond clutch 250 may be configured so that the force exerted by thesecond piston 251 may be controlled by varying the hydraulic pressure orhydraulic fluid in the second hydraulic line 295 from a second hydraulicpump or assembly (not shown). The force from the second piston 251 maydisplace the engaging feature 253, so that the engaging feature 243 isselectively coupled to the coupling member 238 of the ring gear 231.Thus, the second piston 251 of the second clutch 250 may be actuated tocouple the linking member 290 to the ring gear 231 of the PGT 230through the second clutch 250, so that the output torque and power ofthe output shaft 260 are gear-reduced through the PGT 30 relative to theinput torque and power of the input shaft 223.

According to an exemplary embodiment, the output shaft 260 may rotateabout the axis of rotation 221 and may be made of steel or some othersuitable material strong enough to transmit or communicate torque andpower from another component or member of dual gear system 220. Theoutput shaft 260 includes a first end 261 having a torque transmissionfeature 262 to allow for coupling to another vehicle component, such asthe rear axle, to transmit or communicate torque and power. According toan exemplary embodiment, the torque transmission feature 262 may be acountersink having internal splines to engage external splines of ashaft of a mating vehicle component. According to another exemplaryembodiment, the torque transmission feature 262 may be a shaft havingexternal splines to engage the internal splines of a mating vehiclecomponent. The output shaft 260 further includes a second end 265 havinga direct coupling 267 and a gear reduced coupling 266. According to anexemplary embodiment, the direct coupling 267 includes external splinesor gear teeth, which may be engaged by the internal splines of theengaging feature 243. According to an exemplary embodiment, the gearreduced coupling 266 includes external splines or gear teeth, which arecoupled to the internal splines or gear teeth of the gear-reducedcoupling 236 of the carrier 233.

The PGT 230 includes a ring gear 231, a plurality of planet gears 232, acarrier 233, and a sun gear 234. According to an exemplary embodiment,the sun gear 234 is held stationary or fixed, while the ring gear 231provides input power or torque to the PGT 230 through the second clutch250 from the linking member 290, and the carrier 233 providesgear-reduced output power or torque to the output shaft 260. Accordingto an exemplary embodiment, the ring gear 231 may rotate substantiallyabout the axis of rotation 221 and includes internal gear teeth thatengage the plurality of planet gears 232, and a coupling member 238,which has an inner diameter that includes splines or gear teeth that maybe selectively coupled to the second clutch 250. According to anexemplary embodiment, each planet gear 232 includes external gear teeth,which engage the internal gear teeth of the ring gear 231 and theexternal gear teeth of the sun gear 234 simultaneously. Accordingly,each planet gear 232 rotates about an independent pivot axis or its ownaxis of rotation 235. Additionally, each planet gear 232 may include aninner diameter, which may be coupled to the carrier 233. Thus, eachplanet gear 232 rotates about its pivot axis 235 relative to the carrier233, and the plurality of planet gears 232 rotate together with thecarrier 233 about the axis of rotation 221 relative to the sun gear 234.

According to an exemplary embodiment, the carrier 233 includes aplurality of apertures for coupling the plurality of planet gears 232,where each aperture is substantially concentric to the pivot axis 235 ofone of the plurality of planet gears 232. The carrier 233 furtherincludes a gear-reduced coupling 236 having an inner diameter that formsan aperture substantially concentric to the axis of rotation 221 andhaving internal gear teeth coupled to the external gear teeth of thegear-reduced coupling 266 of the output shaft 260. Thus, the carrier 233and output shaft 260 rotate about the axis of rotation 221 withsubstantially the same torque, frequency, and power. According to anexemplary embodiment, the sun gear 234 includes external gear teeth thatengage the external gear teeth of the plurality of planet gears 232, anda fixing member 237 coupled to the housing 229 of the dual gear assembly220, which prohibits rotation of the sun gear 234 relative to thehousing 229.

The dual gear assembly 220 may have three operating configurations. Thefirst configuration is a neutral configuration, where neither the firstclutch 240 nor the second clutch 250 is engaged, so the output shaft 260remains uncoupled and receives no torque or power. The secondconfiguration is a direct connection configuration, where the firstclutch 240 is engaged, but the second clutch 250 is not engaged, so thatthe linking member 290 is coupled to both the direct coupling 267 of thesecond end 265 of the output shaft 260 and to the second end 225 of theinput shaft 223. Thus, the second configuration of dual gear assembly220 outputs substantially the same torque and power relative to thetorque and power that are input into the assembly. The thirdconfiguration is a gear-reduction configuration, where the second clutch250 is engaged, but the first clutch 240 is not engaged, so that thelinking member 290 is coupled to both the coupling member 238 of thering gear 231 of the PGT 230 and to the second end 225 of the inputshaft 223. Thus, the third configuration of the dual gear assembly 220outputs torque and power that are gear-reduced by the PGT 230 relativeto the torque and power that are input into the assembly.

As shown in FIG. 8, another exemplary embodiment of a dual gear assembly320 is illustrated. The dual gear assembly 320 includes a an input shaft323 that is configured to rotate about an axis of rotation 321, at leastone bearing 328, a housing 329, a planetary gear train (PGT) 330, aclutch 340, an output shaft 360 configured to rotate about the axis ofrotation 321, and a linking member 390. According to an exemplaryembodiment, the linking member 390 includes an upper portion 391 and alower portion 392. The upper and lower portions 391, 392 of the linkingmember 390 may be formed separately then rotationally coupled together,such as to include a bearing 328. According to an exemplary embodiment,the input shaft 323 may be made from steel or some other suitablematerial strong enough to transmit or communicate torque from the engineor transmission of a motor vehicle. The input shaft 323 may have anannular shaped first end 324 configured to receive a member thatprovides the input torque and power. The input shaft 323 may furtherinclude an annular shaped second end 325 configured having a differentdiameter. According to an exemplary embodiment, the second end 325 isconnected to the PGT 330. According to an exemplary embodiment, theoutput shaft 360 may be made of steel or some other suitable materialstrong enough to transmit or communicate torque and power, such as fromthe dual gear assembly 320 to another vehicle component or assembly. Theoutput shaft 360 includes a first end 361 having a torque transmissioncoupling to allow for coupling to another vehicle component, such as therear axle, to transmit or communicate torque and power. The output shaft360 also includes a second end 362 having a coupling to receive torque,such as from the PGT 330. The coupling on the second end 362 may beconfigured as external splines configured along the outside diameter ofthe output shaft 360.

The PGT 330 includes a ring gear 331, a plurality of planet gears 332, acarrier 333, and a sun gear 334. According to an exemplary embodiment,the ring gear 331 is connected to the second end 325 of the input shaft323, so that the ring gear 331 provides the input power and torque tothe PGT 330. The ring gear 331 may be formed separately from the inputshaft 323 then coupled to the shaft, such as through welding, or thering gear 331 and the input shaft 323 may be integrally formed. Thus,the ring gear 331 is configured to rotate about the axis of rotation321. According to an exemplary embodiment, the ring gear 331 rotatessubstantially about the axis of rotation 221 and includes internal gearteeth that engage the plurality of planet gears 332. According to anexemplary embodiment, each planet gear 332 includes external gear teeth,which engage the internal gear teeth of the ring gear 331 and theexternal gear teeth of the sun gear 334 simultaneously. Accordingly,each planet gear 332 rotates about an independent pivot axis or its ownaxis of rotation 335. Additionally, each planet gear 232 may include aninner diameter that is substantially concentric with its own axis ofrotation 335, which may be coupled to the carrier 333. Thus, each planetgear 332 may rotate about its pivot axis 335 relative to the carrier333, and the plurality of planet gears 332 may rotate together with thecarrier 333 about the axis of rotation 321, such as relative to the sungear 334.

According to an exemplary embodiment, the carrier 333 includes aplurality of apertures. Each aperture is configured substantiallyconcentric to the pivot axis 335 of one of the plurality of planet gears332, and is configured to couple one planet gear from the plurality ofplanet gears 332. The carrier 333 of the PGT 330 may be rotationallycoupled to the output shaft 360, so that the output shaft 360 rotatesabout the axis of rotation 321 with the same frequency, torque and poweras the carrier 333. For example, the carrier 333 may include an openinghaving internal splines configured to engage external splines on thesecond end 362 of the output shaft 360. The carrier 333 may also beconfigured to selectively couple to the linking member 390 through theclutch 340. According to an exemplary embodiment, the carrier 333includes a direct coupling 367 that is brought into contact with oneplate (or a plurality of plates) of the clutch 340 to induce couplingbetween the carrier 33 and the clutch 340 through friction. The clutch340 may include a piston that controls the plate and hence the amount offriction between the clutch 340 and the carrier 333, thereby controllingwhether the clutch 340 and carrier 333 are coupled or decoupled.

According to an exemplary embodiment, the sun gear 334 includes externalgear teeth that engage the external gear teeth of the plurality ofplanet gears 332. The sun gear 334 may be selectively rotationallycoupled to the linking member 390 through a coupling 385, such as afree-wheel coupling, which may be configured to allow the sun gear 334to rotate about the axis of rotation 321 in one direction only. Forexample, the free-wheel coupling 385 may have a first closed positionthat prohibits free rotation of the sun gear 334 about the axis ofrotation 321, and a second free or open position that allows the sungear 334 to rotate about the axis of rotation 321.

According to an exemplary embodiment, the clutch 340 is configured toselectively couple the linking member 390 to the carrier 333 of the PGT330, so that the linking member 390 may rotate about the axis ofrotation 221 with substantially the same torque and frequency as thecarrier 333. The clutch 340 may include a first open position and asecond closed position. According to an exemplary embodiment, the clutch340 includes a piston that when activated induces the clutch 340 intothe open position, and when the piston is deactivated induces the clutch340 into the closed position.

The dual gear assembly 320 may have three operating configurations. Thefirst configuration is a low gear configuration, where the clutch 340 isconfigured in the open position and the free-wheel coupling 385 isconfigured in the closed position. In the low gear, the sun gear 334 isprohibited from rotating about the axis of rotation 321, so torqueenters the PGT 330 from the input shaft 323 and is transferred in agear-reduced (or gear increased) fashion through the plurality of planetgears 332 and into the carrier 333, which rotates about the axis ofrotation 321 in the same rotational direction as the ring gear 331 (andinput shaft 323), but rotates with a gear-reduced torque. The carrier333 transfers the gear-reduced torque to the second end 362 of theoutput shaft 360, which may then communicate the torque out the firstend 361. The second configuration is a high gear configuration, wherethe clutch 340 is configured in the closed position and the free-wheelcoupling 385 is configured in the free or open position to allow the sungear 334 to rotate about the axis of rotation 321. In the high gear, thering gear 331 (and input shaft 323), the carrier 333, and the pluralityof planet gears 332 rotate about the axis of rotation 321 withsubstantially the same frequency, torque and power. The thirdconfiguration may be a reverse gear configuration, where the clutch 340is configured in the closed position and the free-wheel coupling 385 maybe inactive or configured to be switched off to allow the sun gear 334to rotate in the opposite rotational direction as when in high-gear. Inthe reverse gear configuration, the sun gear 334 and the carrier 333 areconnected, whereby the ring gear 331 (and input shaft 323), the carrier333, and the plurality of planet gears 332 rotate about the axis ofrotation 321 with substantially the same frequency, torque and power.However, each planet gear 332 is configured not to rotate about its axisof rotation 335. The ring gear 331 (and input shaft 323) may inputtorque in the direction opposite to the rotational direction as when inhigh gear, thereby rotating the carrier 333, the plurality of planetgears 332 and the sun gear 334 in the opposite rotational direction(relative to high gear) as well.

The dual gear assemblies 20, 120, 220, 320 may be coupled to the outputof a conventional transmission having a specified number of gear ratios,such as six gear ratios, so that a vehicle having this configurationwould have as the total number of gear ratios, twice the number of gearratios of the conventional transmission. For example, a vehicle having aconventional transmission with six gear ratios coupled to a dual gearassembly disclosed herein would have a total of twelve gear ratios. Theincreased number of gear ratios provide a vehicle with improvedefficiency (e.g., fuel) and with improved power over a broader range ofspeeds. Accordingly, any transmission having any number of specifiedgear ratios may be coupled to a dual gear assembly as disclosed hereinto provide such improvements. Additionally, the dual gear assemblies asdisclosed herein may be coupled directly to the output from the engine,such as the driveshaft.

According to a disclosed embodiment, a gear assembly for a motor vehicleconfigured to provide more than one gear ratio for improved efficiencyis provided. The gear assembly includes a housing for encasing the gearassembly and for providing coupling to the vehicle, an input shaftconfigured to receive an input torque, an output shaft configured totransfer an output torque, a planetary gear train, a linking memberrotationally coupled to the input shaft, and first and second clutchescoupled to the linking member. The input shaft and output shafts, aswell as the linking member, are configured to rotate about an axis ofrotation. The input shaft includes a first end configured to receive aninput torque from a first vehicle component, and a second end configuredto transfer torque. The output shaft includes a first end configured totransmit output torque to a second vehicle component, and a second endto receive torque. The planetary gear train is configured to providegear-reduced (or increased) torque, and includes a ring gear havinginternal gear teeth, a sun gear having external gear teeth, a pluralityof planet gears having external gear teeth, and a carrier havinginternal gear teeth. The external gear teeth of the plurality of planetgears engage the external gear teeth of the sun gear and the internalgear teeth of the ring gear substantially simultaneously. The linkingmember is rotationally coupled to the second end of the input shaft toreceive input torque. The first clutch is configured to selectivelycouple the linking member to the output shaft to transmit torque. Thesecond clutch is configured to selectively couple the linking member tothe planetary gear train to transmit torque to the output shaft throughthe planetary gear train. When the first clutch is activate and thesecond clutch is not activated, the input torque is transmitted from theinput shaft to the output shaft through the linking member, so that theoutput torque relative to the input torque is a first gear ratio. Whenthe second clutch is activated and the first clutch is not activated,the input torque is transmitted from the input shaft to the output shaftthrough the planetary gear train, so that the output torque relative tothe input torque is a second gear ratio. When neither the first clutchnor the second clutch are activated, the input torque is not transmittedfrom the input shaft to the output shaft.

According to another disclosed embodiment, a gear assembly for a motorvehicle configured to provide more than one gear ratio for improvedefficiency is provided. The gear assembly includes a housing forencasing the gear assembly and for providing coupling to the vehicle; aninput shaft configured to rotate about an axis of rotation to transmittorque, wherein the input shaft includes a first end configured toreceive input torque from a first vehicle component and a second endconfigured to transmit torque; and an output shaft configured to rotateabout the axis of rotation to transmit torque, wherein the output shaftincludes a first end configured to transmit output torque to a secondvehicle component and a second end configured to receive torque. Thegear assembly also includes a planetary gear train configured to providegear-reduced (or increased) torque, wherein the planetary gear trainincludes a ring gear having internal gear teeth, a sun gear havingexternal gear teeth, a plurality of planet gears having external gearteeth, and a carrier having internal gear teeth. The external gear teethof the plurality of planet gears engage the external gear teeth of thesun gear and the internal gear teeth of the ring gear substantiallysimultaneously. The gear assembly further includes a slide memberconfigured to rotate about the axis of rotation and rotationally coupledto the second end of the input shaft to receive input torque, whereinthe slide member is configured to slide between a first position and asecond position in a sliding direction relative to the second end of theinput shaft; and a synchronizer assembly rotationally coupled to theoutput shaft to transmit torque to the output shaft, wherein when theslide member is configured at the first position, the slide memberengages the planetary gear train without engaging the synchronizerassembly to transmit torque from the input shaft to the output shaftthrough the slide member and planetary gear train, so that the outputtorque relative to the input torque is a first gear ratio. When theslide member is configured at the second position, the slide memberengages the synchronizer assembly without engaging the planetary geartrain to transmit torque from the input shaft to the output shaftthrough the slide member and the synchronizer assembly, so that theoutput torque relative to the input torque is a second gear ratio. Whenthe slide member is configured between the first and second positions,the slide member neither engages the planetary gear train nor thesynchronizer assembly, and the input torque is not transmitted from theinput shaft to the output shaft.

According to another disclosed embodiment, a gear assembly for a motorvehicle configured to provide more than one gear ratio for improvedefficiency is provided. The gear assembly includes a housing forencasing the gear assembly and an input shaft configured to rotate aboutan axis of rotation to transmit torque. The input shaft includes a firstend configured to receive input torque from a first vehicle componentand a second end configured to transmit torque. The gear assembly alsoincludes an output shaft configured to rotate about the axis of rotationto transmit torque. The output shaft includes a first end configured totransmit output torque to a second vehicle component and a second endconfigured to receive torque. The gear assembly further includes aplanetary gear train configured to receive torque from the second end ofthe input shaft, wherein the planetary gear train includes a ring gearconnected to the input shaft and configured having internal gear teeth,a sun gear having external gear teeth, a plurality of planet gearshaving external gear teeth, and a carrier having internal gear teeth totransmit torque to the output shaft. The external gear teeth of theplurality of planet gears engage the external gear teeth of the sun gearand the internal gear teeth of the ring gear substantiallysimultaneously. The gear assembly also includes a linking memberconfigured to selectively couple to the carrier of the planetary geartrain through a clutch, wherein when the clutch is activated, thelinking member and the carrier rotate together about the axis ofrotation, and the input torque is transmitted from the input shaftthrough the planetary gear train to the output shaft, so that the outputtorque relative to the input torque is a first gear ratio. When theclutch is not activated, the carrier rotates relative to the linkingmember about the axis of rotation, and the input torque is transmittedfrom the input shaft to the output shaft through the planetary geartrain to the output shaft, so that the output torque relative to theinput torque is a second gear ratio.

As utilized herein, the terms “approximately,” “about,” “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like as used herein mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent) or moveable (e.g., removableor releasable). Such joining may be achieved with the two members or thetwo members and any additional intermediate members being integrallyformed as a single unitary body with one another or with the two membersor the two members and any additional intermediate members beingattached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” etc.) are merely used to describe the orientation ofvarious elements in the FIGURES. It should be noted that the orientationof various elements may differ according to other exemplary embodiments,and that such variations are intended to be encompassed by the presentdisclosure.

It is important to note that the construction and arrangement of thedual gear assemblies as shown in the various exemplary embodiments areillustrative only. Although only a few embodiments have been describedin detail in this disclosure, those skilled in the art who review thisdisclosure will readily appreciate that many modifications are possible(e.g., variations in sizes, dimensions, structures, shapes andproportions of the various elements, values of parameters, mountingarrangements, use of materials, colors, orientations, etc.) withoutmaterially departing from the novel teachings and advantages of thesubject matter described herein. For example, elements shown asintegrally formed may be constructed of multiple parts or elements, theposition of elements may be reversed or otherwise varied, and the natureor number of discrete elements or positions may be altered or varied.The order or sequence of any process or method steps may be varied orre-sequenced according to alternative embodiments. Other substitutions,modifications, changes and omissions may also be made in the design,operating conditions and arrangement of the various exemplaryembodiments without departing from the scope of the present invention.

1. A gear assembly for a motor vehicle, comprising: an input shaftconfigured to rotate about an axis of rotation, wherein the input shaftincludes a first end configured to receive input torque from a firstvehicle component and a second end configured to transmit torque; anoutput shaft configured to rotate about the axis of rotation, whereinthe output shaft includes a first end configured to transmit outputtorque to a second vehicle component and a second end configured toreceive torque; a planetary gear train configured to provide outputtorque to the output shaft, wherein the planetary gear train includes aring gear, a sun gear, a plurality of planet gears, and a carrier; afirst clutch configured to selectively couple the input shaft to theoutput shaft to transmit torque; and a second clutch configured toselectively couple the input shaft to the planetary gear train; whereinwhen the first clutch is activated and the second clutch is notactivated, the input torque is transmitted from the input shaft to theoutput shaft such that the output torque relative to the input torque isa first gear ratio; wherein when the second clutch is activated and thefirst clutch is not activated, the input torque is transmitted from theinput shaft to the output shaft through the planetary gear train suchthat the output torque relative to the input torque is a second gearratio; and wherein when neither the first clutch nor the second clutchare activated, the input torque is not transmitted from the input shaftto the output shaft.
 2. The gear assembly of claim 1, further comprisinga linking member rotationally coupled to the input shaft to receiveinput torque from the input shaft and configured to selectively coupleto the first and second clutches.
 3. The gear assembly of claim 1,wherein the planetary gear train is configured to receive torque fromthe linking member when the second clutch is activated through the ringgear, and the planetary gear train is configured to output the gearreduced torque to the output shaft through the carrier.
 4. The gearassembly of claim 3, wherein internal gear teeth of the carrier engageexternal gear teeth of the output shaft to transmit gear-reduced torque.5. The gear assembly of claim 3, wherein the sun gear is fixed to thehousing and the gear teeth of sun gear engage the gear teeth of theplurality of planet gears.
 6. The gear assembly of claim 5, wherein thegear teeth of each planet gear also engage the internal gear teeth ofthe ring gear.
 7. The gear assembly of claim 1, wherein each planet gearincludes a pivot axis concentric to an aperture in the carrier allowingfor rotation of each planet gear about its pivot axis relative to thecarrier.
 8. The gear assembly of claim 5, wherein the plurality ofplanet gears are configured to rotate together with the carrier aboutthe axis of rotation.
 9. The gear assembly of claim 1, wherein the firstgear ratio is substantially
 1. 10. The gear assembly of claim 1, whereinthe first vehicle component is a component selected from the groupconsisting of a transmission, an engine, a gear, and a frontdifferential of a motor vehicle.
 11. The gear assembly of claim 1,wherein the second vehicle component is a component selected from thegroup consisting of a rear differential, a rear axle, and a gear of amotor vehicle.
 12. The gear assembly of claim 1, wherein the planetarygear train is configured to receive input torque through the sun gearfrom the linking member when the second clutch is activated, and theplanetary gear train is configured to provide output torque to theoutput shaft through the carrier.
 13. The gear assembly of claim 12,wherein the ring gear is fixed to the housing and the gear teeth of thering gear engage the gear teeth of the plurality of planet gears. 14.The gear assembly of claim 1, wherein the planetary gear train isconfigured to receive input torque through the sun gear from the linkingmember when the second clutch is activated, and the planetary gear trainis configured to provide output torque to the output shaft through thering gear.
 15. The gear assembly of claim 14, wherein the carrier isfixed to a housing.
 16. A gear assembly for a motor vehicle, comprising:an input shaft including a first end configured to receive input torquefrom a first vehicle component and a second end configured to transmittorque; an output shaft including a first end configured to transmitoutput torque to a second vehicle component and a second end configuredto receive torque; a planetary gear train including a ring gear, a sungear, a plurality of planet gears, and a carrier; and a slide memberrotationally coupled to the input shaft to receive input torque; whereinthe slide member is configured to slide between a first position and asecond position in a sliding direction relative to the second end of theinput shaft; wherein at the first position, the slide member engages theplanetary gear train to transmit torque from the input shaft to theoutput shaft through the slide member and planetary gear train such thatthe output torque relative to the input torque is a first gear ratio;wherein at the second position, the slide member engages the outputshaft without engaging the planetary gear train to transmit torque fromthe input shaft to the output shaft through the slide member such thatthe output torque relative to the input torque is a second gear ratio;wherein when the slide member is between the first and second positions,the slide member engages neither the planetary gear train nor the outputshaft, and the input torque is not transmitted from the input shaft tothe output shaft.
 17. The gear assembly of claim 16, further comprisinga synchronizer assembly rotationally coupled to the output shaft andconfigured to selectively engage the slide member when the slide memberis in the second position.
 18. The gear assembly of claim 16, whereinthe planetary gear train is configured to receive torque from the slidemember through the ring gear when in the first position, and theplanetary gear train is configured to output torque to the output shaftthrough the carrier.
 19. The gear assembly of claim 18, wherein thecarrier of the planetary gear train is integrally formed with the secondend of the output shaft.
 20. The gear assembly of claim 18, wherein thesun gear is fixed to the housing and the external gear teeth of sun gearengage the external gear teeth of the plurality of planet gears.
 21. Thegear assembly of claim 20, wherein the external gear teeth of eachplanet gear also engage the internal gear teeth of the ring gear. 22.The gear assembly of claim 16, wherein each planet gear includes a pivotaxis concentric to an aperture in the carrier allowing for rotation ofeach planet gear about its pivot axis relative to the carrier.
 23. Thegear assembly of claim 16, further comprising an actuator assemblyconfigured to slide the slide member from the first position to thesecond position.
 24. The gear assembly of claim 23, wherein the actuatorassembly includes an actuator that couples to the slide member, suchthat movement of the actuator moves the slide member substantially thesame distance.
 25. The gear assembly of claim 24, wherein the actuatorassembly includes a piston configured to induce a force on the actuatorto move the actuator when activated.
 26. The gear assembly of claim 23,wherein the actuator assembly includes a biasing member configured toimpart a force in the direction opposing the force from the piston. 27.A gear assembly for a motor vehicle, comprising: an input shaftconfigured to rotate about an axis of rotation; an output shaftconfigured to rotate about the axis of rotation; a planetary gear trainconfigured to receive torque from the input shaft, wherein the planetarygear train includes a ring gear connected to the input shaft, a sungear, a plurality of planet gears, and a carrier configured to transmitoutput torque; and a clutch configured to selectively couple the outputshaft and the planetary gear train; wherein when the clutch isactivated, the output shaft and the carrier rotate together about theaxis of rotation, and the input torque is transmitted from the inputshaft through the planetary gear train to the output shaft, so that theoutput torque relative to the input torque is a first gear ratio;wherein when the clutch is not activated, the carrier is decoupled fromthe output shaft but the sun gear is coupled to the output shaft, andthe input torque is transmitted from the input shaft to the output shaftthrough the planetary gear train, so that the output torque relative tothe input torque is a second gear ratio.
 28. The gear assembly of claim27, further comprising a linking member rotationally coupled to theinput shaft to receive input torque from the input shaft, and configuredto selectively couple to the clutch.